1. Field
The disclosed concept relates generally to electrical switching apparatuses and, more particularly, to circuit interrupters.
2. Background Information
One type of electrical switching apparatus is a circuit interrupter. Circuit interrupters, such as for example and without limitation, circuit breakers, are typically used to protect electrical circuitry from damage due to an overcurrent condition, such as an overload condition, a short circuit, or another fault condition, such as an arc fault or a ground fault. Circuit breakers typically include primary separable contacts. The primary separable contacts may be operated either manually by way of a handle disposed on the outside of the case or automatically in response to a detected fault condition. Typically, such circuit breakers include an operating mechanism, which is designed to rapidly open and close the primary separable contacts, and a trip mechanism, such as a trip unit, which senses a number of fault conditions to trip the breaker automatically. Upon sensing a fault condition, the trip unit trips the operating mechanism to a trip state, which moves the separable contacts to their open position.
One type of circuit breaker is a remote circuit breaker. Remote circuit breakers typically include separable contacts which may be operated by a controller. In some remote circuit breakers, the separable contacts are provided as secondary separable contacts operated by the controller along with primary separable contacts operated by a trip unit. Remote circuit breakers can be used, for example, to control lights in stores and office buildings that must turn on or off at certain times of the day. Those times can be programmed into the controller that operates the secondary contacts.
In one remote circuit breaker configuration, coupling and uncoupling of the separable contacts is controlled through the operation of a bi-directional solenoid. The bi-directional solenoid is operated in a first direction to push an operating mechanism to uncouple the separable contacts, and then the bi-directional solenoid is operated in a second opposite direction to pull the operating mechanism to couple the separable contacts.
Bi-directional solenoids require two sets of coils around an actuator in order to support bi-direction operation. Uni-directional solenoids, on the other hand, only require a single set of coils around the actuator. In applications where space is limited (e.g., without limitation, small or miniature circuit breakers), the space for a solenoid is limited, and thus, the total number of coils that can be wrapped around the actuator in the solenoid is limited. Given the same total number of coils around the actuator and the same amount of power, a uni-directional solenoid is able to operate the actuator with more force than a bi-directional solenoid because all the coils in the uni-directional solenoid can be used to apply force to the actuator in a single direction. However, a uni-directional solenoid is not suitable for use with the above-described remote circuit breaker because the operating mechanism requires both pushing and pulling.
There is room for improvement in electrical switching apparatuses.
There is also room for improvement in circuit interrupters.